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Pvat-piston Valve Air Tank

Update Pg. 4- 3/4" tank

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#26 Hubb

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Posted 08 March 2010 - 01:22 PM

I like this design. It's very similar to a Nelson type valve (if any of you know what that is). In fact, it's similar to the one I'm designing now. I'm interested to see it completed, though, especially how you plan on triggering it. An option (if you haven't decided already) is to use the actual bolt to open the valve.

As far as the QEV, yes these can perform well if they are set up correctly. I'd assume that since you are using this type of valve, that you are already familiar with this, so I won't go into any details on it. They are a bit less efficient than spool valves of similar size, but it should work okay if the pressure in the chamber is right, which is going to depend on it's volume and the actual function of the blaster.
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#27 Lt Stefan

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Posted 08 March 2010 - 02:51 PM

@minsc- I have not seen those threads but they look someone similar. However the second one is too long of a design for my tastes. A more war legal version may come in the form of a 3/4" tank which I hope to build today.

@Hubb- I'm not sure I know what you mean, "how I plan on triggering it." It's like an at2k tank, pop it in somewhere and get a wire and keyring. Hopefully I can make an actual gun out of this with polycarb though.....

On a side note I have a question. I know the whole PVC cement is needed to hold pressure thing, but this thing isn't reaching higher pressures than in a Nerf gun and I've found that CA holds just as well as PVC cement when it comes to bonding plastics, especially PVC. After all, it does do the same thing: melt the pieces of plastic together. Do you think that is okay to glue the couplers on with?

-EDIT-

For some reason today I pumped it and it didn't leak after five pumps, but the oprv on the pump started kicking in anyway. Also another thing to note is when the system is pressurized any slight tap to the exposed bolt results in a loss of pressure. Hopefully Bob's method will fix this. I should have updates later tonight.

Edited by Lt. Stefan, 08 March 2010 - 03:47 PM.

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#28 Lt Stefan

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Posted 08 March 2010 - 04:24 PM

Well what does? The thing is when I put it on the PVC it actually starts to melt the printed words on the side...
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#29 Draconis

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Posted 08 March 2010 - 05:05 PM

Well what does? The thing is when I put it on the PVC it actually starts to melt the printed words on the side...


Plummin: Ur doin it rong.
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#30 Lt Stefan

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Posted 08 March 2010 - 05:11 PM

I thought CA is a solvent weld.... If it is not what is?
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#31 Ice Nine

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Posted 08 March 2010 - 05:37 PM

I thought CA is a solvent weld.... If it is not what is?


It's cyanoacrylate. It loves bonding with water which is why it does better with porous materials or a slightly dampened surface. It is essentially a resin.

It does not solvent weld because it isn't a solvent.
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#32 Lt Stefan

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Posted 08 March 2010 - 05:49 PM

Then what does? And would this take the place of PVC cement?

Edited by Lt. Stefan, 08 March 2010 - 05:49 PM.

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#33 zaphodB

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Posted 08 March 2010 - 05:53 PM

Use pvc cement to connect pvc together. Tools are specialized for a reason.
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#34 Draconis

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Posted 08 March 2010 - 06:06 PM

Then what does? And would this take the place of PVC cement?



You don't actually understand the concept of solvent welding, do you? Look at Zorn's guide to solvent welding.
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#35 Lt Stefan

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Posted 08 March 2010 - 06:33 PM

Which solvent do you recommend besides PVC cement then?

Edited by Lt. Stefan, 08 March 2010 - 08:49 PM.

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#36 Split

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Posted 08 March 2010 - 08:08 PM

Man, either you're really confused and partially illiterate (which is a valid possibility) or you're trolling your own thread.

Let me lay it out as simply as possible for you:
CA/Superglue/cyanoacrylate: Not for holding pressure, even though it may. Not a solvent weld.
Solvent welding/PVC cement (yes, these are the same thing): Will melt the plastic together, should be used for making pressure-safe pvc tanks.

Now, with that in mind, re-read the last few posts and realize how stupid you look. Hope that clears everything up for you.

Oh, and nifty proof of concept tank.

Edited by Split, 08 March 2010 - 08:09 PM.

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#37 Lt Stefan

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Posted 08 March 2010 - 08:48 PM

CA/Superglue/cyanoacrylate: Not for holding pressure, even though it may. Not a solvent weld.
Solvent welding/PVC cement (yes, these are the same thing): Will melt the plastic together, should be used for making pressure-safe pvc tanks.


I realize that's what PVC cement does. Maybe it wasn't clear enough, but I wanted to know what else besides PVC cement would work.

Edited by Lt. Stefan, 08 March 2010 - 08:48 PM.

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#38 Lt Stefan

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Posted 08 March 2010 - 09:03 PM

Thank you JSB this is just the information I need...
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#39 Zorns Lemma

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Posted 08 March 2010 - 11:57 PM

Thank you JSB this is just the information I need...


I don't know why you would want something other than PVC cement though. All the products that Bob listed are either going to be more dangerous than PVC cement, or in the same isle, on the same shelf, right next to the cans of PVC cement.

Your best bet for alternative methods of solvent-welding would be to use paint stripper/thinner or pure acetone. Of course, all this info is in the thread on solvent welding: http://nerfhaven.com/forums/index.php?showtopic=18527

Edited by Zorn's Lemma, 08 March 2010 - 11:59 PM.

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#40 Lt Stefan

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Posted 09 March 2010 - 12:07 AM

Okay thanks everyone, I know have all the information I need on the solvents.

An update:

I started work on the 3/4" tank which should be done by tomorrow. I'll have to use a flat 1/2" washer because everything else is too big for the fitting I'm using. I'm pretty sure if I have a long enough barrel though that should give the air time to get around the the >1/8" of space there is between the washer and the interior wall of the PVC.


Improvements to 1" Rev.3:
-Put metal washer behind rubber one for reinforcement
-Use flat faucet washer as spring rest in concert with the two o-rings.

Edited by Lt. Stefan, 09 March 2010 - 12:09 AM.

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#41 VACC

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Posted 09 March 2010 - 08:23 AM

Your best bet for alternative methods of solvent-welding would be to use paint stripper/thinner or pure acetone. Of course, all this info is


...wrong


If you can correct something Zorn has said, feel free to do so in a civil manner. Giving an, essentially, binary response in order to display your superiority is just fucking annoying.
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#42 Lt Stefan

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Posted 09 March 2010 - 04:19 PM

McMaster Parts list for Rev.2, anyone (mostly courtesy of RazgrizInferno on NR)? Includes everything but the 5/8L beveled washer; you'll have to go to Ace hardware for that.

48925K93 – 1” PVC
4880K53 – 1” PVC Endcap
4880K73 – 1” PVC Coupler
4880K314 – 1” x 1/2” Reducer
94115K008 – O-rings
92356A564 – 5 1/2” x ” Carriage Bolt
91845A029 – 1/4” Hex nuts
9657K222 – Spring
9117T113 – Vinyl Tubing
5372K511 – Vinyl tubing fitting

I switched out the bolt for 5" one in my next design. As a rule the spring should be one inch shorter than the bolt length and the rate should be less than 10 lbs/inch. So if you made one with a 6" bolt find a spring that's 5" long.


EDIT
The bolt there is fully threaded and I can't find one that isn't so DON'T order that bolt. Just go to Lowes anyway it's easier. And get their hex bolts, they seem slightly thicker and make a better seal as I found out.

Edited by Lt. Stefan, 09 March 2010 - 05:53 PM.

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#43 Draconis

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Posted 09 March 2010 - 07:36 PM

You know... You could use plain steel rod, and push nuts instead of a bolt and threaded nuts.
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#44 Lt Stefan

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Posted 09 March 2010 - 08:11 PM

You could do that. I got some so I can thread it for a bigger size airtank, but why would you need to for the small ones? Bolts work perfectly fine.
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#45 Lt Stefan

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Posted 09 March 2010 - 08:23 PM

I find that the amount of work it would take to prepare a steel rod would make buying bolts more effective.
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#46 Draconis

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Posted 10 March 2010 - 02:40 PM

I find that the amount of work it would take to prepare a steel rod would make buying bolts more effective.



Except that with rod, you get a uniform extrusion, and no chance of damaging the o-rings on the threads. Bolts are cast, and often have casting artifacts.
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#47 Lt Stefan

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Posted 10 March 2010 - 03:19 PM

I used a needle nose pliers to open up the o-ring wide enough to slide down the bolt without touching the threads. Also I sanded the sliding part down and it's very smooth.
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#48 Zorns Lemma

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Posted 10 March 2010 - 04:14 PM

I used a needle nose pliers to open up the o-ring wide enough to slide down the bolt without touching the threads. Also I sanded the sliding part down and it's very smooth.


I'm pretty sure that together takes more effort than simply buying the right components and assembly everything onto steel rod...
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#49 Lt Stefan

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Posted 10 March 2010 - 06:12 PM

Then use a steel rod if you want to. I'm not stopping you.
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#50 Lt Stefan

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Posted 10 March 2010 - 09:40 PM

Legit DP:

I finished the 3/4" tank. Power is definitely decreased, but it is still very strong. A video will be up tomorrow.

Posted Image

The finished product. it's pretty small.

Posted Image

I tried Bob's back sealing idea. Seems to be holding up well, but it increases the strength needed to open the valve a LOT.

Posted Image

I put a metal washer behind the metal one for reinforcement.

Posted Image

Seems to fit nicely. I used a 1/2 beveled washer and shaved 1/32" of rubber off the sides to allow for air to get through faster.

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